Nanomaterials2013, 3(4), 615-637; doi:10.3390/nano3040615 - published online 26 November 2013 Show/Hide Abstract
Abstract: Molecular imprinting is a well-established technology to mimic antibody-antigen interaction in a synthetic platform. Molecularly imprinted polymers and nanomaterials usually possess outstanding recognition capabilities. Imprinted nanostructured materials are characterized by their small sizes, large reactive surface area and, most importantly, with rapid and specific analysis of analytes due to the formation of template driven recognition cavities within the matrix. The excellent recognition and selectivity offered by this class of materials towards a target analyte have found applications in many areas, such as separation science, analysis of organic pollutants in water, environmental analysis of trace gases, chemical or biological sensors, biochemical assays, fabricating artificial receptors, nanotechnology, etc. We present here a concise overview and recent developments in nanostructured imprinted materials with respect to various sensor systems, e.g., electrochemical, optical and mass sensitive, etc. Finally, in light of recent studies, we conclude the article with future perspectives and foreseen applications of imprinted nanomaterials in chemical sensors.
Nanomaterials2013, 3(4), 606-614; doi:10.3390/nano3040606 - published online 15 November 2013 Show/Hide Abstract
Abstract: Tin-oxide and graphene (TG) composites were fabricated using the Electrostatic Spray Deposition (ESD) technique, and tested as anode materials for Li-ion batteries. The electrochemical performance of the as-deposited TG composites were compared to heat-treated TG composites along with pure tin-oxide films. The heat-treated composites exhibited superior specific capacity and energy density than both the as-deposited TG composites and tin oxide samples. At the 70th cycle, the specific capacities of the as-deposited and post heat-treated samples were 534 and 737 mA·h/g, respectively, and the corresponding energy densities of the as-deposited and heat-treated composites were 1240 and 1760 W·h/kg, respectively. This improvement in the electrochemical performance of the TG composite anodes as compared to the pure tin oxide samples is attributed to the synergy between tin oxide and graphene, which increases the electrical conductivity of tin oxide and helps alleviate volumetric changes in tin-oxide during cycling.
Nanomaterials2013, 3(4), 592-605; doi:10.3390/nano3040592 - published online 28 October 2013 Show/Hide Abstract
Abstract: The formation of gold microparticles on a silicon substrate through the use of energetic surface plasmons is reported. A laser-assisted plasmonics system was assembled and tested to synthesize gold particles from gold thin film by electrical field enhancement mechanism. A mask containing an array of 200 nm diameter holes with a periodicity of 400 nm was prepared and placed on a silicon substrate. The mask was composed of 60 µm thick porous alumina membrane sputter-coated with 100 nm thin gold film. A Nd:YAG laser with 1064 nm wavelength and 230 µs pulse width (free-running mode) was then passed through the mask at an energy fluence of 0.35 J/cm2. The extraordinary transmission of laser light through alumina/gold micro-hole optical antenna created both extended and localized surface plasmons that caused the gold film at the bottom of the mask to fragment into microparticles and deposit on the silicon substrate that is in direct contact with the mask. The surface plasmon method is simpler, quicker, more energy efficient, and environmentally safer than existing physical and chemical methods, as well as being contamination-free, and can be extended to all types of materials that will in turn allow for new possibilities in the formation of structured surfaces.
Nanomaterials2013, 3(4), 583-591; doi:10.3390/nano3040583 - published online 24 October 2013 Show/Hide Abstract
Abstract: Phase and size of lanthanide-doped nanoparticles are the most important characteristics that dictate optical properties of these nanoparticles and affect their technological applications. Herein, we present a systematic study to examine the effect of alkaline earth doping on the formation of NaYF4 upconversion nanoparticles. We show that alkaline earth doping has a dual function of tuning particle size of hexagonal phase NaYF4 nanoparticles and stabilizing cubic phase NaYF4 nanoparticles depending on composition and concentration of the dopant ions. The study described here represents a facile and general strategy to tuning the properties of NaYF4 upconversion nanoparticles.
Nanomaterials2013, 3(4), 574-582; doi:10.3390/nano3040574 - published online 15 October 2013 Show/Hide Abstract
Abstract: This investigation studies CoFeB/AlOx/Co magnetic tunneling junction (MTJ) in the magnetic field of a low-frequency alternating current, for various thicknesses of the barrier layer AlOx. The low-frequency alternate-current magnetic susceptibility (χac) and phase angle (θ) of the CoFeB/AlOx/Co MTJ are determined using an cac analyzer. The driving frequency ranges from 10 to 25,000 Hz. These multilayered MTJs are deposited on a silicon substrate using a DC and RF magnetron sputtering system. Barrier layer thicknesses are 22, 26, and 30 Å. The X-ray diffraction patterns (XRD) include a main peak at 2θ = 44.7° from hexagonal close-packed (HCP) Co with a highly (0002) textured structure, with AlOx and CoFeB as amorphous phases. The full width at half maximum (FWHM) of the Co(0002) peak, decreases as the AlOx thickness increases; revealing that the Co layer becomes more crystalline with increasing thickness. χac result demonstrates that the optimal resonance frequency (fres) that maximizes the χac value is 500 Hz. As the frequency increases to 1000 Hz, the susceptibility decreases rapidly. However, when the frequency increases over 1000 Hz, the susceptibility sharply declines, and almost closes to zero. The experimental results reveal that the mean optimal susceptibility is 1.87 at an AlOx barrier layer thickness of 30 Å because the Co(0002) texture induces magneto-anisotropy, which improves the indirect CoFeB and Co spin exchange-coupling strength and the χac value. The results concerning magnetism indicate that the magnetic characteristics are related to the crystallinity of Co.
Nanomaterials2013, 3(4), 572-573; doi:10.3390/nano3040572 - published online 14 October 2013 Show/Hide Abstract
Abstract: This Special Issue of Nanomaterials is focused on the continuing implementation of nanomaterials and nanostructures in the development of more sensitive and more specific sensing devices. As a result, these new devices employ smaller sensing elements and provide more “real time” capability. Often, the inclusion of nanomaterials leads to sensing elements for targets that were previously inaccessible.